This extension lets you send now playing data from any supported website (youtube, soundcloud, spotify (web), etc.) to the Universal Now Playing desktop app.
Install the extension from the Chrome Web Store, if you're not using Chrome, Firefox/Edge builds will be uploaded soon, the browsers themselves should already be supported, so you can build the extension and use it like that if you wish.
To build, just install the dependencies (npm i/yarn) and then run the build script for the browser that you are testing on, for example, npm run build:chrome.
I anticipate most changes to be related to src/worker-es6.js, that is the script that is injected into a web page when you press the "Use on this page" button.